Whats good against Advent-antifighter spam ?

skarovas enforcers i suppose

I believe standard light frigates (i.e. skirmishers) are best against anti-sc frigates.

Flak Frigates have heavy armour, and the only unit in the game that has an advantage against heavy is the light frigate.  Unfortunately, Vasari has the worst light frigate of any faction, the Skirmisher.  It's very expensive, but pound-for-pound both the Disciple and Cobalt hit much harder.  As well, you're very vulnerable to enemy LRF with this unit (though not so much the Advent Illuminator).  Aside from that, enforcers will work.  They don't receive any penalties when attacking light armor, and their very heavy armor makes them close to impervious to the flak frigate's damage. 

The bottom line, though, is that the Vasari faction's best units are all the phase missile units, and flaks force you to counter with units that don't use phase missiles, so this strategy inherently forces you to build your worst unit types, making you easier to counter overall.  You can fill out your force with your Sentinels, which do use phase missiles and will help counter enemy LRF as well as fighters and bombers. 

an Anti-Air unit countering a Long-Range unit... who came up with this? that's like saying a SAM site or an AA gun killed enemy artillery imo makes no sence. but ya with my friend he loves flak and those ARE heavily armoured and can improve staying time and drag out a battle, you want heavy units against them. Late game subverters help too (but then again they ALWAYS help )

long-range frigate armor is pretty thin, similar to strikecraft armor, since fighters also counter lrf pretty well... in Sins anyway.

This one goes back to the very early days of Sins.  It was well known before I even arrived on the scene in early 2009.

Flaks actually have pretty good overall damage output, and their overall durability is superb, all for a very low cost.  They're a great unit, and just because their primary purpose is anti-strike craft doesn't mean they can't be used for other purposes.

I would build 2 or if you can 3 skirantras and micromanage repair cloud ability all abilities would be off. This way you can repair your assailants constantly and given time when skirantras get to bigger levels you wont loose single assailant anymore. Eventually you will overwhelm him. and force him to start building something else. 

It was done to me plenty of times by star player and if done correctly its really hard to defend against.

Make sure you do all armor and hull research you can though.....

well, thats just the opness of the skirantra...

against flak spam yes but skirantras had repair cloud since beginning of time and you do need to be very good in microing to pull it off. I'm not a complete noob and actually I don't have problems being accepted into skilled games .... but against a skilled player so far I couldn't manage to do it the way star does it against me all the time 

PS: If you want balanced caps seluecia has some threads in which he wants opinion on abilities .... for his ultimate balance mod. Don't know how successful he is though.

Actually, no one complained about the Skirantra before 1.19, and repair cloud is really no stronger than it's ever been. 

Using repair cloud is easier said than done, because it's a relatively short range ability.  The enemy will be able to get their LRF in range, making it difficult to get the Skirantra out alive.  Greg is very right that this is hard to pull off, especially against skilled opponents.  Very nice when you do pull it off, however, especially against flaks or illuminators.

Repair Cloud... Just another "excuse" for us Advent to use Detonate Antimatter.

And at least in this case, you should be able to get close enough to do it.  You'll have a hard time catching a Skirantra if it's kiting and scrambling.

Only trouble is focus fire; Advent has a lot of trouble keeping capital ships alive versus Vasari, and a front-liner like the Radiance more than anything.